Pink diamonds are amongst the rarest and most sought after of all and The Vivid Pink is one of the most fabulous examples imaginable.

Weighing in at an impressive 5.0 carats, the diamond is cushion-cut and apparently flawless, with no secondary colour. It has been set in a simple ring, allowing its beauty to speak for itself.

Whilst most colour variations from colourless diamonds are caused by trace elements, such as boron for blue diamonds, the cause of the hues in pink diamonds remains mysterious to chemists.

The Vivid Pink has qualified for a rating as Fancy Vivid by the Gemological Institute of America. Only one in 100,000 diamonds has colour deep enough to qualify for this description, but it will be of no surprise to anyone who's seen the diamond that its mesmerising hue is up to the standard.

The gem is expected to sell for $5-7m (HK$39- $55m) in Hong Kong on December 1 2009, but will go on a tour round the world first.

The tour will include New York: October 17-20, Singapore: October 29-30, Bangkok: November 11-12, Geneva: November 15-17, Taipei: November 21-22 and then finally Hong Kong from November 27.

There are few examples of really high quality gemstones to invest in, so the chance to see or own a stone as beautiful as The Vivid Pink is not to be missed.